Biology XII Content
The Human Heart
The human heart is a hollow, cone-shaped muscular organ located between the two lungs above the diaphragm. Two-thirds of the heart is located to the left of the mid line of the body and 1/3 is to the right.
In heart, the apex points down and to the left. It is 5 inches (12 cm) long, 3.5 inches (8-9 cm) wide and 2.5 inches (6 cm) from front to back, and is roughly the size of one’s fist. The heart comprises less than 0.5 percent of the total body weight.
Internal Layers of Heart:
The heart has three layers. The smooth, inside lining of the heart, made of epithelial tissues, is called the endocardium. The middle layer of heart muscle is called the myocardium, which is made of cardiac muscles and important part of the heart. It is surrounded by a fluid filled sac call the pericardium, which is outermost part.